Internal combustion engines have traditionally been installed such that the transfer of engine vibrations and noise to the surrounding structures is kept as small as easily possible. Normally this is achieved by mounting the engine by means of resilient rubber mounts on the mounting frame of the power plant or of the vehicle, be it a car, a truck or a marine vessel. Lately, the demands for further lessening the vibrations and noise has resulted in improving the insulation degree by moving the natural frequencies further away from excitation frequencies. This has been done by reducing the stiffness of the mounting system, i.e. the engine mounts. Thus, soft engine mounts are therefore needed in applications with strict vibration and noise requirements. However, firstly, soft engine mounts as such inevitably results in heavy movement of the engine during operation and requires special attention. And secondly, when using soft rubber mounts the creep rate is high and frequent re-alignment of the engine is needed, which is a costly and time consuming task for the engine operator.
As an example of prior art documents that at least partially touch upon the above discussed problems JP-A-2002019475 may be mentioned. The JP document discloses the use of engine mounts each having an air chamber, which is partitioned by a diaphragm. In accordance with the JP document the characteristics of the engine mounts are adjusted by means of changing the volume of their air chambers simultaneously by supplying air therein or exhausting air therefrom. The air chambers are arranged to be in communication with either the atmospheric air or the air intake passage between the throttle valve and the engine. A change over valve controls the communication of the air chambers such that the air chambers may be emptied or filled when needed. The operational status of the engine, like rotational speed, the position of the gas pedal etc. dictates whether the gas chambers are to be emptied or filled. The basic idea is that when the engine is in idle operation the engine mounts are set to soft position, i.e. gas chambers are filled with gas, and when the engine is in its non-idle operating condition the engine mounts are set to hard position i.e. gas is discharged from the air chambers.
Though the hydraulic and/or pneumatic engine mounts of prior art may not share the problem of soft rubber mounts, i.e. the high creep rate requiring regular re-alignment of the engine, they do not pay any attention to possible changes in the alignment of the engine between different operational conditions.
Thus, an object of the present invention is to introduce a novel arrangement of mounting an internal combustion engine such that its alignment is maintained in all operational conditions of the engine.
Another object of the present invention is to introduce a novel method of maintaining the alignment of an internal combustion engine while the engine is running.
Yet another object of the present invention is to introduce a novel method of aligning an internal combustion engine it is mounted and maintaining its alignment while the engine is running.